Effect and mechanism of intermittent myocardial ischemia induced by exercise on coronary collateral formation

Molecular insights of exercise therapy in disease prevention and treatment

Despite substantial evidence emphasizing the pleiotropic benefits of exercise for the prevention and treatment of various diseases, the underlying biological mechanisms have not been fully elucidated. Several exercise benefits have been attributed to signaling molecules that are released in response to exercise by different tissues such as skeletal muscle, cardiac muscle, adipose, and liver tissue. These signaling molecules, which are collectively termed exerkines, form a heterogenous group of bioactive substances, mediating inter-organ crosstalk as well as structural and functional tissue adaption. Numerous scientific endeavors have focused on identifying and characterizing new biological mediators with such properties. Additionally, some investigations have focused on the molecular targets of exerkines and the cellular signaling cascades that trigger adaption processes. A detailed understanding of the tissue-specific downstream effects of exerkines is crucial to harness the health-related benefits mediated by exercise and improve targeted exercise programs in health and disease. Herein, we review the current in vivo evidence on exerkine-induced signal transduction across multiple target tissues and highlight the preventive and therapeutic value of exerkine signaling in various diseases. By emphasizing different aspects of exerkine research, we provide a comprehensive overview of (i) the molecular underpinnings of exerkine secretion, (ii) the receptor-dependent and receptor-independent signaling cascades mediating tissue adaption, and (iii) the clinical implications of these mechanisms in disease prevention and treatment.

Effects of exercise training in hypoxia versus normoxia on fat-reducing in overweight and/or obese adults: A systematic review and meta-analysis of randomized clinical trials

Objective: Fat loss theory under various oxygen conditions has been disputed, and relevant systematic review studies are limited. This study is a systematic review and meta-analysis to assess whether hypoxic exercise training (HET) leads to superior fat-reducing compared with normoxic exercise training (NET).

Methods: We searched PubMed, Web of Science, CNKI, ProQuest, Google Scholar, Cochrane Library, and EBSCOhost from inception to June 2022 for articles comparing the effects of hypoxic and normoxic exercise on body composition indicators, glycometabolism, and lipometabolism indicators in obese and overweight adults. Only randomized controlled trials (RCTs) were included. The effect sizes were expressed as standardized mean difference (SMD) and 95% confidence intervals (CI). Between-study heterogeneity was examined using the I² test and evaluated publication bias via Egger’s regression test. The risk of bias assessment was performed for each included trial using Cochrane Evaluation Tool second generation. The meta-analysis was performed by using R 4.1.3 and RevMan 5.3 analytic tools.

Results: A total of 19 RCTs with 444 subjects were analyzed according to the inclusion and exclusion criteria. Among them, there were 14 English literature and five Chinese literature. No significant difference in body composition (SMD -0.10, 95% CI -0.20 to -0.01), glycometabolism and lipid metabolism (SMD -0.01, 95% CI -0.13 to -0.10) has been observed when comparing the HET and NET groups. We only found low heterogeneity among trials assessing glycometabolism and lipometabolism (I² = 20%, p = 0.09), and no publication bias was detected.

Conclusion: The effects of HET and NET on fat loss in overweight or obese people are the same. The application and promotion of HET for fat reduction need further exploration.

High intensity interval training exercise as a novel protocol for cardiac rehabilitation program in ischemic Egyptian patients with mild left ventricular dysfunction

Background

Exercise-based Cardiac rehabilitation (CR) plays a major role in reducing mortality and morbidity in patients with coronary artery disease (CAD). The standard protocol is usually of moderate intensity exercise. High-intensity interval training (HIIT) consists of alternating periods of intensive aerobic exercise with periods of passive or active moderate/mild intensity recovery.

Aim

This study aimed to assess HIIT program for ischemic patients attending CR after percutaneous coronary intervention (PCI) who have mild left ventricular dysfunction and to compare its effect on the functional capacity and quality of life with standard exercise CR program.

Patients and methods

Our study included 40 patients with documented CAD, who participated in the outpatient CR program in Ain Shams University hospital (Al-Demerdash Hospital) divided into two equal groups, each included 20 patients. Group A included the patients who underwent standard cardiac rehabilitation program, while group B joined the high intensity interval training exercise protocol.

Results

Groups A and B showed significant improvement in all items of comparison; especially functional capacity, lipid profile and quality of life. Group B showed better improvements in the emotional well-being items of QOL parameters.

Conclusion

We emphasize the positive effects of exercise-based CR program on patients with CAD and mild left ventricular dysfunction after PCI. The novel high intensity cardiac training proved to be safe and at least as beneficial as the standard moderate intensity cardiac training protocols, with better quality of life improvement.

Cardioprotective Exercise and Pharmacologic Interventions as Complementary Antidotes to Cardiovascular Disease

Exercise and pharmacologic therapies to prevent and treat cardiovascular disease have advanced largely through independent efforts. Understanding of first-line drug therapies, findings from preclinical animal studies, and the need for research initiatives related to complementary cardioprotective exercise-pharma interventions are reviewed from the premise that contemporary cardioprotective therapies must include adjunctive exercise and lifestyle interventions in addition to pharmacologic agents.

Calcitonin gene-related peptide in aerobic exercise induces collateral circulation development in rat ischemia myocardium

PURPOSE

Aerobic exercise may offer favorable effects for coronary perfusion in the myocardial ischemia area, although the underlying molecular mechanisms remain unclear. This study was designed to investigate the effect of aerobic exercise on the collateral circulation in the ischemia myocardium and to evaluate calcitonin gene-related peptide (CGRP) changes during this process.

METHODS AND RESULTS

Wistar rats were randomly divided into 3 groups of 7 rats each: a sham operated group (Sham), a myocardial ischemia-only group (MI) and a MI plus aerobic exercise group (MI+AE). The rat myocardial ischemia model was established by injecting isoprenaline (2mg/kg, i.p.). The aerobic exercise training consisted of swimming (40min/d, 5d/wk) for 4 weeks. At the end-points, after echocardiographic analysis was performed, blood and ischemia myocardium samples were collected and analyzed by ELISA to quantify the CGRP protein. The dorsal root ganglia were isolated and analyzed by reverse transcription polymerase chain reaction (RT-PCR) to examine the CGRP mRNA expression, and ischemia myocardium capillary density was evaluated by immunohistochemistry. Our data showed that the capillary density in the left ventricle and heart function were significantly decreased with decreased CGRP production in the MI rats, which were reversed by aerobic exercise in the MI+AE rats.

CONCLUSION

These results indicate that aerobic exercise may alleviate myocardial ischemia through collateral circulation development with increased CGRP production. CGRP may play an important role in developing the collateral circulation.

Effect of High Interval Training in Acute Myocardial Infarction Patients with Drug-Eluting Stent

OBJECTIVE

Peak oxygen uptake (VO2peak) is a strong predictor of survival in cardiac patients. The aims of this study were to compare the effects of high interval training (HIT) to moderate continuous training (MCT) on VO2peak and to identify the safety of HIT in acute myocardial infarction patients with drug-eluting stent.

DESIGN

Twenty-eight acute myocardial infarction patients with drug-eluting stent were randomized to either HIT at 85%-95 % of heart rate reserve or MCT at 70%-85% of heart rate reserve, 3 days a week for 6 wks at a cardiac rehabilitation clinic. Primary outcome was VO2peak at baseline and after cardiac rehabilitation.

RESULTS

Both HIT and MCT groups showed significant increases in VO2peak and heart rate recovery after 6 wks of training. The 22.16% improvement in VO2peak in the HIT group was significantly greater than the 8.48% improvement in the MCT group (P = 0.021). There were no cardiovascular events related to both HIT and MCT.

CONCLUSIONS

HIT is more effective than MCT for improving VO2peak in acute myocardial infarction patients with drug-eluting stent. These findings may have important implications for more effective exercise training in cardiac rehabilitation program.

The evolving concept of physiological ischemia training vs. ischemia preconditioning

Ischemic heart diseases are the leading cause of death with increasing numbers of patients worldwide. Despite advances in revascularization techniques, angiogenic therapies remain highly attractive. Physiological ischemia training, which is first proposed in our laboratory, refers to reversible ischemia training of normal skeletal muscles by using a tourniquet or isometric contraction to cause physiologic ischemia for about 4 weeks for the sake of triggering molecular and cellular mechanisms to promote angiogenesis and formation of collateral vessels and protect remote ischemia areas. Physiological ischemia training therapy augments angiogenesis in the ischemic myocardium by inducing differential expression of proteins involved in energy metabolism, cell migration, protein folding, and generation. It upregulates the expressions of vascular endothelial growth factor, and induces angiogenesis, protects the myocardium when infarction occurs by increasing circulating endothelial progenitor cells and enhancing their migration, which is in accordance with physical training in heart disease rehabilitation. These findings may lead to a new approach of therapeutic angiogenesis for patients with ischemic heart diseases. On the basis of the promising results in animal studies, studies were also conducted in patients with coronary artery disease without any adverse effect in vivo, indicating that physiological ischemia training therapy is a safe, effective and non-invasive angiogenic approach for cardiovascular rehabilitation. Preconditioning is considered to be the most protective intervention against myocardial ischemia-reperfusion injury to date. Physiological ischemia training is different from preconditioning. This review summarizes the preclinical and clinical data of physiological ischemia training and its difference from preconditioning.

Impact of remote physiological ischemic training on vascular endothelial growth factor, endothelial progenitor cells and coronary angiogenesis after myocardial ischemia

OBJECTIVE

This experimental study investigates the potential role of physiological ischemic training (PIT) of remote limbs on vascular endothelial growth factor (VEGF), endothelial progenitor cells (EPCs) and myocardial angiogenesis after myocardial ischemia.

METHODS

Forty-two rabbits were assigned into six groups at random: sham-operated (SO), training only (TO), myocardial ischemia (MI), PIT, EPC promoter (PIT+), and EPC inhibitor (PIT-). MI was experimentally induced by implanting a constrictor around the left ventricular branch. The PIT procedure included three 3-min cycles of cuff inflations on the hind limbs followed by a 5 min reperfusion. VEGF mRNA, protein and EPC numbers were measured in plasma and myocardium. Capillary density (CD), coronary blood flow (CBF) and coronary collateral blood flow (CCBF) were also determined.

RESULTS

Groups were compared using non-parametric statistics and associations between agents were explored with fractional polynomial regression. VEGF-mRNA and -protein levels were highest in PIT+ and PIT. PIT differed significantly from SO, TO, MI, and PIT- regarding VEGF-mRNA and -protein in plasma and VEGF-protein in myocardium. EPCs were highest in PIT+ followed by PIT. PIT differed significantly from SO, TO, MI, and PIT- regarding plasma EPCs. CD, CCBF and CCBF/CBF were significantly increased in PIT+ and PIT as compared to controls. PIT- did not differ significantly from SO and TO. VEGF explained up to 43% of variance in EPCs. EPCs explained up to 87% of variance in CD. CD explained up to 97% of variance in CCBF and CCBF/CBF.

CONCLUSION

PIT stimulates VEGF-mediated mobilization of EPCs as well as angiogenesis and might be proven as a new treatment strategy for patients with coronary heart disease.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis

BACKGROUND/AIM

Cardiorespiratory fitness (CRF) is a strong determinant of morbidity and mortality. In athletes and the general population, it is established that high-intensity interval training (HIIT) is superior to moderate-intensity continuous training (MICT) in improving CRF. This is a systematic review and meta-analysis to quantify the efficacy and safety of HIIT compared to MICT in individuals with chronic cardiometabolic lifestyle diseases.

METHODS

The included studies were required to have a population sample of chronic disease, where poor lifestyle is considered as a main contributor to the disease. The procedural quality of the studies was assessed by use of a modified Physiotherapy Evidence Base Database (PEDro) scale. A meta-analysis compared the mean difference (MD) of preintervention versus postintervention CRF (VO2peak) between HIIT and MICT.

RESULTS

10 studies with 273 patients were included in the meta-analysis. Participants had coronary artery disease, heart failure, hypertension, metabolic syndrome and obesity. There was a significantly higher increase in the VO2peak after HIIT compared to MICT (MD 3.03 mL/kg/min, 95% CI 2.00 to 4.07), equivalent to 9.1%.

CONCLUSIONS

HIIT significantly increases CRF by almost double that of MICT in patients with lifestyle-induced chronic diseases.

Role of exercise in the prevention of cardiovascular disease: results, mechanisms, and new perspectives

On an empirical basis, exercise has been regarded as a fundamental pre-requisite for human well-being and physical integrity since classical times. Only in the last decades, however, scientific evidence has accumulated proving its role in the prevention and treatment of multiple chronic diseases beyond any reasonable doubt. Few treatment strategies in medicine have been tested so rigorously in large cohorts of patients as regular physical exercise. With the advent of molecular biology, the underlying mechanisms, such as NO bioavailability and mobilization of progenitor cells, could be identified. This enhances our understanding of this therapeutic tool. Unfortunately, the low compliance rate of the patients is the major drawback of the intervention exercise training (ET). The objective of this manuscript is to summarize the current knowledge with respect to ET on cardiovascular disease (CVD) and the molecular changes elicited by ET. Finally, we will critically assess reasons why ET as therapeutic option is not as effective at the population level in preventing CVD and what we may change in the future to make ET the most effective intervention to fight the development of CVD.

High-intensity interval training in cardiac rehabilitation

High-intensity interval training (HIIT) is frequently used in sports training. The effects on cardiorespiratory and muscle systems have led scientists to consider its application in the field of cardiovascular diseases. The objective of this review is to report the effects and interest of HIIT in patients with coronary artery disease (CAD) and heart failure (HF), as well as in persons with high cardiovascular risk. A non-systematic review of the literature in the MEDLINE database using keywords 'exercise', 'high-intensity interval training', 'interval training', 'coronary artery disease', 'coronary heart disease', 'chronic heart failure' and 'metabolic syndrome' was performed. We selected articles concerning basic science research, physiological research, and randomized or non-randomized interventional clinical trials published in English. To summarize, HIIT appears safe and better tolerated by patients than moderate-intensity continuous exercise (MICE). HIIT gives rise to many short- and long-term central and peripheral adaptations in these populations. In stable and selected patients, it induces substantial clinical improvements, superior to those achieved by MICE, including beneficial effects on several important prognostic factors (peak oxygen uptake, ventricular function, endothelial function), as well as improving quality of life. HIIT appears to be a safe and effective alternative for the rehabilitation of patients with CAD and HF. It may also assist in improving adherence to exercise training. Larger randomized interventional studies are now necessary to improve the indications for this therapy in different populations.

High-intensity aerobic interval training in a patient with stable angina pectoris

Recently, high-intensity aerobic interval training was shown to be more effective than continuous moderate-intensity exercise for improving maximal aerobic capacity and endurance in patients with coronary heart disease. However, patients with exercise-induced ischemia were not included in those studies. We present the acute cardiopulmonary responses of a 67-yr-old man with stable angina pectoris during a 34-min session of high-intensity aerobic interval training. Exercise was well tolerated with neither significant arrhythmia nor elevation of cardiac troponin-T. We observed a complete disappearance of symptoms and signs of myocardial ischemia after 24 mins of exercise. This observation is similar to the warm-up angina phenomenon, an adaptation to myocardial ischemia that remains poorly understood. We conclude that high-intensity aerobic interval training is a promising mode of training for patients with stable coronary heart disease that should also be investigated further in patients with exercise-induced ischemia.

Redox-sensitive Akt and Src regulate coronary collateral growth in metabolic syndrome

We have recently shown that the inability of repetitive ischemia (RI) to activate p38 MAPK (p38) and Akt in metabolic syndrome [JCR:LA-cp (JCR)] rats was associated with impaired coronary collateral growth (CCG). Furthermore, Akt and p38 activation correlated with optimal O(2)(-). levels and were altered in JCR rats, and redox-sensitive p38 activation was required for CCG. Here, we determined whether the activation of Src, a possible upstream regulator, was altered in JCR rats and whether redox-dependent Src and Akt activation were required for CCG. CCG was assessed by myocardial blood flow (microspheres) and kinase activation was assessed by Western blot analysis in the normal zone and collateral-dependent zone (CZ). RI induced Src activation (approximately 3-fold) in healthy [Wistar-Kyoto (WKY)] animals but not in JCR animals. Akt inhibition decreased (approximately 50%), and Src inhibition blocked RI-induced CCG in WKY rats. Src inhibition decreased p38 and Akt activation. Myocardial oxidative stress (O(2)(-). and oxidized/reduced thiols) was measured quantitatively (X-band electron paramagnetic resonance). An antioxidant, apocynin, reduced RI-induced oxidative stress in JCR rats to levels induced by RI in WKY rats versus the reduction in WKY rats to very low levels. This resulted in a significant restoration of p38 (approximately 80%), Akt (approximately 65%), and Src (approximately 90%) activation in JCR rats but decreased the activation in WKY rats (p38: approximately 45%, Akt: approximately 65%, and Src: approximately 100%), correlating with reduced CZ flow in WKY rats (approximately 70%), but significantly restored CZ flow in JCR rats (approximately 75%). We conclude that 1) Akt and Src are required for CCG, 2) Src is a redox-sensitive upstream regulator of RI-induced p38 and Akt activation, and 3) optimal oxidative stress levels are required for RI-induced p38, Akt, and Src activation and CCG.